Guadalupe Gutierrez Gutierrez

This paper introduces an extended Stochastic Finite-Difference Time-Domain (S-FDTD) method tailored to analyze thin panel structures. It aims to predict the standard deviation and probability density function (PDF) of electromagnetic magnitudes (fields and currents), assuming their uncertainties in geometrical and material parameters are both known. The method to account for the sub-cell nature of the thin panel method used is based on the broadly tested subgridding boundary condition (SGBC) approach. This method employs an implicit-explicit hybrid (HIE) scheme in an unconditional Crank-Nicolson (CN) formulation (CN-SGBC), ensuring that it does not introduce any extra limitations to the standard stability criterion of the FDTD method. In the article, classical models of explicit formulations of S-FDTD are extended to the CN-SGBC HIE formulation.

The direct current injection (DCI) technique is a complicated method which involves both a testing campaign and electromagnetic simulations. Consequently, it takes a long time, entails high costs, and requires a lot of effort in a complex post-process. The present article shows that only with the lightning simulations, also involved in the DCI process, similar and useful information can be obtained. Currents induced on cables in a lightning simulation on an aircraft cockpit are compared with the postprocessed results coming from a low-level DCI test, demonstrating good agreement within the established margin, and analyzing the identified differences. This example illustrates the benefits of using simulations in reducing costs and delivery time. We also show their potential benefit in improving the aircraft safety by using them from the earlier stages of the design to the end of service of the aircraft. This is achieved thanks to their capability to predict the behavior of the object in configurations which could not be addressed by test, and by checking a larger number of probes, which could even be placed in non-accessible areas.

Presents corrections to the paper, “HIRF virtual testing on C-295 aircraft validated with FSV method,” (Gutierrez, G.G., et al), IEEE Trans. Electromagn. Compat., vol. 56, no. 4, pp. 854–863, Aug. 2014.

Electrical and electronic systems on board air vehicles are susceptible to electromagnetic interference (EMI). This has made the topic of electromagnetic compatibility (EMC), a major concern for aircraft safety. The use of composite materials worsens this situation, for their poor shielding and low conductive capabilities. Some of the main experimental E3 certification scenarios used in aeronautics are revisited in this chapter. Guidelines to achieve simple, yet accurate, numerical models of them are provided, with appropriate tradeoffs between computational simplicity and accuracy. The numerical method, endowed with extended capabilities, has been chosen for this task for its ability and efficiency to deal with complex problems of arbitrary materials. The feature selective validation (FSV) IEEE standard procedure, commonly used to quantify the comparison of data in electromagnetic problems, is also revisited. The simulation of three different air vehicles in several certification scenarios is finally described and the numerical results compared to experimental data.

The increased use of carbon-fiber composites in unmanned aerial vehicles is a challenge for their EMC assessment by numerical solvers. For accurate and reliable simulations, numerical procedures should be tested not only for individual components, but also within the framework of complete systems. With this aim, this paper presents a benchmark test case based on experimental measurements coming from direct-current injection tests in the SIVA unmanned air vehicle, reproduced by a numerical finite-difference-time-domain solver that employs a new subgridding scheme to treat lossy composite thin panels. Validation was undertaken by applying the feature selective validation method, which quantifies the agreement between experimental and numerical data.

A novel conformal technique for the FDTD method, here referred to as Conformal Relaxed Dey-Mittra method, is proposed and assessed in this letter. This technique helps avoid local time-step restrictions caused by irregular cells, thereby improving the global stability criterion of the original Dey-Mittra method. The approach retains a second-order spatial convergence. A numerical experiment based on the NASA almond has been chosen to show the improvement in accuracy and computational performance of the proposed method.

As part of the technology research engaged in the EU Clean Sky 1 project, we present in this paper an electrical structure network (ESN) designed to prevent the impact on an electronic equipment of unwanted voltage drops appearing when nonmetal composite materials are used for grounding. An iterative process has been followed to reach an optimal tradeoff solution meeting all the aircraft requirements: structural, safety, low weight, electrical, etc. Guidelines on the design of a low-impedance metal ESN, to minimize the inductive behavior of the power distribution network, are outlined in this paper. To this end, we employ the UGRFDTD simulation tool, combining finite-difference time domain to analyze the general EM problem, and a multiconductor transmission-line network to handle internal coupling between cables running along coinciding routes. The capability of this tool to create time-domain snapshots of surface currents is shown to provide a useful way to optimize the ESN, thanks to the insight gained on the physics of the problem.

In the last years, different works on reverberant microwave propagation and high frequency coupling inside oversized structures have been published in order to make progress in the investigation of wireless systems and electromagnetic threats. In this paper, a new focus to the shielding effectiveness (SE) prediction using the reverberation microwave propagation formalism has been applied to a real complex object attaining very good agreement with the measured data obtained from nested reverberation chamber method. The used formalism is the combination of the simplified propagation model with the updated and more accurate formulation for cavity Q-factor and energy dissipation mechanisms. A very wide frequency range, from 500 MHz to 40 GHz, has been analyzed, which allows us to draw conclusions about how each parameter affects the final SE result at different frequency bands. Furthermore, a tuning study has been performed taking into account the tolerance in the most important parameters, such as the cavity size, the Q-factor, the main dissipation energy mechanisms, and the aperture shapes.